Datasonics has developed and tested a two-way acoustic telemetry link with
software/firmware for command, control, and recovery of data from an (RDI)
acoustic Doppler current profiler (ADCP) instrument. In operation, the acoustic
link is quasitransparent to the system operator. Standard ADCP user command
protocol allows PC-generated commands to be buffered and transmitted from a
surface acoustic modem to a subsurface modem, which is connected by RS-232
interface cable to the ADCP. The acoustic down link command signals are
reformatted in the subsurface modem and passed on to the ADCP. Data are
transmitted over the up-link in 4096-byte packets at a data rate of 1200
bits/s. The self-contained subsurface acoustic telemetry modem (ATM) is housed
in an aluminum pressure housing 5 in. o.d.x33 in. long. Connectors are provided
for RS-422 I/O to the ADCP and for external power input for long-term in situ
deployments. A choice of directional or omni directional acoustic transducers
is available. The system was tested in the Piscatagua River in Portsmouth, NH
and will be installed in Tampa Bay as part of NOAA's PORTS program, which
offers shipping traffic access to current profiler data in near real time. The
operating software protocol will be discussed and results from both the New
Hampshire tests and Tampa Bay operations will be presented.